The present invention is directed to a roll hardening apparatus used to surface or deep harden workpieces such as cam shafts and particularly crankshafts having main bearings and pin bearings. As described in U.S. Pat. No. 5,493,761, it is common in current crankshaft roll hardening machines to mount a rolling device such as a rolling head in a fixed position at the end of each of a pair of scissor action type lever arms having a common pivot and to open and close the scissor levers with hydraulic cylinder devices. That is, the hydraulic cylinder devices pivot the upper ends of the scissor lever arms to close and to clamp the hardening rollers of the rolling heads onto the respective bearing to be rolled and conversely, to pivot the upper ends of the scissor lever arms apart to a clearance or release position so that the rolling heads are disengaged from the crankshaft bearings for then being shifted away from the working area via advancing and retracting suspension devices to allow removal of the finished crankshaft and replacement with a new crankshaft to be rolled. Such an arrangement is shown in U.S. Pat. No. 5,943,893. The scissor lever arms are suspended by the suspension devices that allow the scissor lever arms to oscillate and follow the movement of a pin bearing as it travels eccentrically about the rotational axis of the crankshaft.
It will be appreciated that the main bearings and pin bearings on a crankshaft, particularly for automotive vehicles and trucks, are closely spaced, and that the scissor lever arms, their suspension devices and their hydraulic cylinder devices which can be quite elaborate and complex, thus have to be crowded into a small space. For example, the crankshaft rolling machine disclosed in U.S. Pat. No. 5,943,893 includes an angled bellcrank lever that is pivotally connected to the suspension device and to one of the respective scissor arms that cooperates to allow opening of the jaws defined between the respective rolling tools to a width that is greater than twice the maximum radius of the crankshaft. To assist the positioning of the scissor lever arms for loading and unloading of crankshafts front and rear vertical guide surfaces are provided on the stationary frame, one at the front of the frame via vertical spars and the other toward the rear of the frame via housings for the suspension devices, and along which roll rollers on the upper ends of the scissor lever arms.
A large number of hydraulic cylinders are used in the rolling machine disclosed in U.S. Pat. No. 5,943,893 to shift the scissor arms and to apply the rolling force. There are hydraulic cylinder devices that operate to shift the scissor arms through a long travel stroke, another hydraulic cylinder to open and close the roller heads, and yet another hydraulic cylinder shifts the scissor arms and rolling heads to apply the roll hardening force to the crankshaft.
Further, each of these hydraulic devices is pivotally mounted to various of the operating components for moving the scissor arms. In all, fourteen distinct pivot points for each set of scissor arms can be identified. And when there are ten such sets of arms, the machine will have one-hundred-and-forty pivot connections for the scissor-rolling arms. As is apparent, where the crankshaft bearings are very closely spaced, the number of the cylinders and their diameter sizing will make it very difficult to have the cylinders all fit in a compact fashion on one side of the crankshaft without staggering axially adjacent cylinders from each other, or separating the arms that roll the pin bearings from those used to roll the mains such as in the aforementioned '761 patent and as shown in U.S. Pat. No. 5,138,859. Also, the large number of pivotally mounted cylinders provide potential failure points due to the high number of moving parts and pivot points which may wear and cause seizing of parts. Accordingly, the reliability and maintainability of the '893 machine is significantly impaired by the large number of pivotal cylinders it employs. In other words, a machine that needs so many cylinders and pivot connections is much more prone to failure and will require more in the way of maintenance attention and expenses than is desirable.
From the foregoing, it will be seen that there is a need for an improved, high-production rolling method and apparatus that is simpler than the scissor action machines and yet is able to roll harden crankshafts or the like with the high quality required and at the high production speeds needed for automotive vehicles. More specifically, there is a need for an apparatus and method that simplifies the closing of the rolling heads into rolling engagement with the crankshaft bearings and subsequent opening of the heads. Preferably, the rolling parts will be suspended in a manner that allows them to be shifted in the axial direction to either roll other bearings on the same crankshaft or to be repositioned to roll bearings on other longer or shorter length crankshafts that have their respective bearings at different spacings such as in the aforementioned '761 patent which is incorporated herein by reference.